Mobile communications devices are rapidly becoming the preferred instrument for mass communications. With the resulting demand, a need has arisen for improved methods of manufacturing these devices. In particular the housings for these devices must be manufactured with greater efficiency while affording greater impact resistance at a lower cost.
Impact extrusion is a well established method of manufacture which allows the cold forming of metal parts into a wide variety of shapes. In this process a wide variety of shapes can be formed in a fast, simple and repeatable manner. Impact extrusion involves the placement of a slug of metal into a die and forcing a punch into the die. The metal slug is rendered plastic by the impact and flows around the periphery of the punch. A part results which has an external shape in the form of the die and an internal shape in the form of the punch. It has been found that this method works with a variety of metals, for example, aluminum, zinc, gold, steel, magnesium, titanium, copper, and an assortment of alloys. Aluminum is generally preferred.
It is a purpose of this invention to employ impact extrusion to manufacture the housings for mobile communications devices. This would replace the present production methods which involve coining/pressing mating halves of a housing. One method in use constructs the mating housing parts by means of deep drawing. In this method the halves are formed, aligned and joined together by laser welding. The parts often are distorted by spring back. The edges of the parts need to be trimmed to size causing scratching of the finish. This requires further finishing by plasting or other means which adds to the risk of distortion. This makes the joining process difficult and after joining, extensive finishing is required to hide the weld lines and the resulting marking of the finish, i.e. by blasting and polishing. It is a purpose of this invention to provide a more economical process for constructing these parts.
A method is performed in which a housing for a mobile communications device is constructed. The steps include constructing a slug of metal selected from aluminum or appropriate alloy. Placing the slug for further processing in a reverse impact extrusion die. Constructing the die having a generally rectangular cross section. Constructing a punch with a shape which is matched to fit into the die with a predetermined clearance. Impacting the slug to cause the slug to become plastic and flow around the punch to fill the clearance. Thereby forming a single piece housing having a thickness consistent with the clearance. The impact extruded housing is then cold worked in an ironing step to form the housing with a final shape and finish. The die is constructed with grooves or rails to provide an attachment mechanism for side grip panels.